When a small mass-produced permanent magnet electric D.C. motor is manufactured, it will have a certain amount of shaft endplay, meaning that the shaft can be displaced axially relative to the housing. Heretofore it has been the typical practice to perform an endplay adjustment as a separate step after the shaft has been assembled to the housing. Such an adjustment can be internal or external. It involves measuring the amount of endplay, selecting a device of appropriate thickness, such as a clip, washer, etc., and assembling the device onto the motor such that the device will limit the shaft endplay to a tolerable amount.
The present invention relates to a method of making a motor which eliminates the need for a separate endplay adjustment. The invention relies in part upon a certain positioning of the motor's permanent magnets during their assembly into one part of the motor housing which results in the magnets' force acting on the motor shaft in a manner that urges the shaft in one direction along the shaft's axis so that the entire endplay is caused to appear at only one end of the shaft. In this way the shaft is properly axially located so that the existence of endplay in whatever amount is actually present will not result in the axial position of the shaft relative to the housing being outside a specified tolerance during motor operation. The elimination of a separate endplay adjustment saves on time, labor, and materials in the assembly of such motors.
The invention will be disclosed with reference to the ensuing description which is accompanied by drawings illustrating the best mode contemplated at this time for carrying out the invention.